`filter': iptables who? (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.

 

make menuconfig

按顺序

networking
networking options
network packet filtering framework (Netfilter)
Core Netfilter Configuration

选中Netfilter connection tracking support
Exit
IP:Netfilter Configuration
选中Ipv4 connection tracking support(requited for NAT)
选中Full NAT
Exit
最后保存
然后编译
make

重启后挂载2个模块
modprobe nf_nat_pptp
modprobe nf_nat_proto_gre
然后再测试。ok了